1. Field of the Invention
The present invention relates to a device for detecting partial discharges in an electrical apparatus placed in a tank filled with oil, wherein the tank wall is provided with at least one drain tap.
Belonging to the category of such apparatus are inter alia generator, coupling and distribution transformers of large capacity. These are placed in a tank filled with oil.
Other categories of apparatus which are placed in a tank filled with oil, such as compensating coils, are however by no means excluded.
2. Description of the Related Art
In order to determine the quality of operation of such an apparatus, particularly in respect of the quality of the applied insulation materials and deriving therefrom the anticipated operating time until a subsequent failure and the remaining life expectancy, the detection of partial discharges is of the greatest importance. Partial discharges often represent the prelude to destructive processes in such an apparatus.
According to presently known electrical measuring techniques, use is made of an apparatus wherein the transformer is taken out of operation, the transformer is placed in a measuring arrangement and a measurement is then performed. It is possible herein for such a measurement also to be carried out during operation. In order to arrange the measuring equipment and remove it after the measurement has been performed, the transformer must however be taken out of operation. It will be apparent that this is less than desirable on account of the economic consequences of taking a transformer out of operation, particularly when it is a generator transformer.